This invention relates to the field of frustrated total internal reflection devices and more particularly to a frustrated total internal reflection switch using double pass reflection and method of operation.
Fiber-optic communication systems include optical components, such as optical fibers coupled to switching components, that receive, transmit, and otherwise process information in optical signals. The switching components in a fiber-optic communication system selectively direct the information carried by the optical signal to one or more other optical components. A problem with existing fiber-optic communication systems is that a portion of the information in the optical signal may not reach its intended destination. One reason for this is that the optical signal experiences some loss or leakage during the switching operations due to imperfections in the optical components, or in the switch actuation device, that cause the optical signal to reflect in an undesired manner. The undesired signals produced as a result of these problems are commonly referred to as cross-talk. There is a need in the field of fiber-optic communication systems to reduce the effects of cross-talk.
One attempt to reduce cross-talk in fiber-optic communication systems requires the optical components and actuation devices to be manufactured according to precise specifications having small tolerances for error. A drawback to this approach is that manufacturing optical components and actuation devices according to strict specifications is expensive, time-consuming, and sometimes unattainable. When the small tolerances are not realized in the optical components, the result is a misaligned signal or cross-talk. There is therefore a need in the field of fiber-optic communications to relax the precise manufacturing specifications of optical components while reducing the effects of cross-talk.
A frustrated total internal reflection switch using double pass reflection is provided that substantially eliminates or reduces disadvantages and problems associated with previous optical switches.
In accordance with one embodiment of the present invention, an optical switch for processing an optical signal includes a refractive material having a first surface, a second surface, and a third surface. The optical switch also includes a lens having a planar surface that is coupled to the third surface of the refractive material and a convex surface. The optical switch further includes a switchplate coupled to the second surface of the refractive material. The switchplate has a first position spaced apart from the second surface such that the second surface totally internally reflects optical signal toward the convex surface of the lens, and the second surface totally internally reflects the optical signal reflected by the convex surface to a first output optical device. The switchplate has a second position in proximal contact with the second surface to frustrate the total internal reflection of the optical signal such that the switchplate totally internally reflects the optical signal toward the convex surface of the lens, and the switchplate totally internally reflects the optical signal reflected by the convex surface toward a second output optical device.
Another embodiment of the present invention is a method for processing an optical signal that includes receiving the optical signal at a first surface of a refractive material. The optical signal diverges as it propagates toward the first surface of the refractive material. The method continues by totally internally reflecting the optical signal at a second surface of the refractive material toward a lens coupled to the third surface of the refractive material, wherein the lens comprises a convex surface. The method continues by reflecting the optical signal at the convex surface toward the second surface of the refractive material. The method concludes by totally internally reflecting the optical signal at the second surface of the refractive material such that the optical signal converges toward an output optical device.
Yet another embodiment of the present invention is an optical switch for processing an optical signal that includes a refractive material having a first surface, a second surface, and a third surface. A collimating lens couples to the first surface of the refractive material. A first decollimating lens couples to the first surface of the refractive material. A second decollimating lens couples to the first surface of the refractive material. A switchplate couples to the second surface of the refractive material and has a first position spaced apart from the second surface such that the second surface totally internally reflects a collimated beam toward the third surface of the refractive material and the second surface totally internally reflects the collimated beam reflected by the third surface to a first output optical device coupled to the first decollimating lens. The switchplate has a second position in proximal contact with the second surface to frustrate the total internal reflection of the collimated beam such that the switchplate totally internally reflects the collimated beam toward the third surface and the switchplate totally internally reflects the collimated beam reflected by the third surface toward a second output optical device coupled to the second decollimating lens.
A technical advantage of the present invention includes one embodiment of a frustrated total internal reflection optical switch that includes a refractive material, a switchplate coupled to the refractive material, and a lens with a convex surface that reflects a diverging input optical signal such that it converges toward an output optical device. This particular embodiment of the optical switch eliminates the use of collimating and decollimating lenses so that the optical switch can be constructed using fewer components which may reduce the packing density of the switch.
While in a switched state, the switchplate of the optical switch is typically placed in proximal contact with a surface of the refractive material to frustrate the total internal reflection of the optical signal. A small portion of the optical signal may be totally internally reflected, however, at the surface of the refractive material and processed as though the switch is operating in the unswitched state. This undesired result is commonly referred to as a cross-talk signal. The negative effects of the cross-talk signal are realized if an optical device of the switch receives and further processes the cross-talk signal.
Another technical advantage offered by the present invention is that the optical switch reduces the effects of a cross-talk signal. In particular, the optical switch of the present invention further processes any cross-talk signals so that a large portion of the cross-talk signal is not received by an optical device of the optical switch. The negative effects of the cross-talk signal are thereby reduced. For example, in the switched state, a cross-talk signal resulting from residual reflection at the interface between a surface of the refractive material and the switchplate is reflected back by the lens toward the switchplate. The switchplate placed in proximal contact with the surface of the refractive material frustrates the total internal reflection of most of the cross-talk signal reflected by the lens such that the signal is totally internally reflected by a reflective surface of the switchplate away from any optical devices.
Upon reflection by the lens, only a small, residual portion of the original optical signal is totally internally reflected at the interface between the surface of the refractive material and the switchplate as though the switch was operating in the unswitched mode. Therefore, only a negligible portion of the original optical signal, if any, comprises a cross-talk signal that may actually reach an optical device of the switch. Thus, the cross-talk signal is dissipated and its effects become negligible. The reduction in the magnitude of the cross-talk signal in the present invention will be referred to as a cross-talk improvement and generally results from the repeated reflection of the optical signal at the interface between the refractive material and the switchplate. Such a repeated reflection of the optical signal described above will be generally referred to as a xe2x80x9cdouble pass reflection.xe2x80x9d
Another important advantage of the optical switch relates to the cross-talk improvement described above. Generally, the cross-talk signal described above is generated as a result of imperfections in the components of the optical switch, such as imperfections in the surfaces of the switchplate and the refractive material, or in less than ideal actuator performance which results in a slight air gap at the interface between the switchplate and prism. By reducing the magnitude of cross-talk signals to acceptable levels during the operation of the optical switch using the double pass reflection technique described above, manufacturing tolerances for the components used in the switch may be increased, and components are thus easier and less costly to manufacture. For example, the surface of the refractive material and the switchplate may be constructed with increased surface roughness and still meet industry standards in reducing the effects of cross-talk. Also, components having a larger degree of environmental contamination can be used, and still provide acceptable cross-talk performance during the operation of the switch. Furthermore, operational tolerances for components of the optical switch, such as the actuator, may be increased.
In addition to supporting increased manufacturing tolerances for optical components, the double pass reflection techniques of the present invention allows actuator performance requirements to be relaxed. For example, the degree of proximal contact to which the actuator brings the switchplate and the surface of the refractive material may be relaxed and still provide acceptable cross-talk performance during the operation of the switch.
The convex surface of the lens in the optical switch reflects a diverging input optical signal such that it converges at a focal point. The position of the focal point is based upon a radius of curvature of the convex surface of the lens, the thickness of the switchplate, or both depending upon the mode of operation. The output optical device intended to receive the output optical signal should be substantially coincident with the focal point of the signal so that the device can receive a maximum amount of the signal. In prior fiber-optic communication systems, once the switch is manufactured, the positions of the output optical devices are fixed based upon a calculated position for the focal point of the optical signal. Manufacturing defects associated with components of which the switch is constructed may cause the actual focal point to be somewhere other than the calculated position of the focal point so that the output optical devices of the switch are misaligned.
Another technical advantage of the present invention is the use of tuning spacers that overcome misalignment problems associated with prior optical switches. In particular, the tuning spacers of the present invention may position the output optical devices of the switch even after the switch is manufactured. Thus, even if the precise specifications of the optical components have not been met, causing a deviation in the focal point of the signal and resulting in misalignment of the output devices, a tuning spacer may controllably position an output optical device substantially coincident with the actual focal point of an output optical signal. Furthermore, should the connections in the optical switch loosen due to jarring or prolonged operation, the tuning spacers support the periodic repositioning of the output optical devices so as to avoid the expense of replacing the switch.
Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.